Astronomers have found a new clutch of tiny, dense galaxies that thrived in the early universe. But they still can’t explain why the compact objects are nowhere to be found today.
The ultra-dense galaxies, which were already full of old stars when the universe was less than 3 billion years old, were first reported in 2008. The most extreme have masses that rival the Milky Way’s, but are just one-tenth as wide.
“They’re packing essentially as much mass as the normal galaxies that we see around us today in [a volume] about a thousand times smaller,” says Alan Stockton of the University of Hawaii in Honolulu.
Using the Keck II Telescope on Mauna Kea in Hawaii, Stockton and colleagues have found new examples of these galaxies at distances of about 11 billion light years away. Stockton presented images of the objects on Tuesday at a meeting of the American Astronomical Society in Pasadena, California.
The galaxies are so massive and some have such fragile disc shapes that they seem to have formed directly from the collapse of massive clouds of matter instead of being built up gradually by a series of mergers of smaller objects, Stockton says.